Small-scale Geodiversity Regulates Functioning, Connectivity, and Productivity of Shrubby, Semi-arid Rangelands

Geodiversity has recently been attracting increasing attention as a measure of diversity for the physical components of natural environments. It has shown positive relations with biodiversity, as well as with several ecosystem services. Yet, so far, geodiversity studies have focused on relatively large spatial scales, ranging between hillslope, basin, and landform scales. It is proposed that either natural-induced or anthropogenic-induced, small-scale (centimeter-scale to few decimeter-scale) geodiversity has a large impact on the hydrological connectivity and overall functioning of semi-arid rangelands and other shrubby and woody drylands. It is further proposed that greater small-scale geodiversity increases the on-site retention of water and soil resources, decreasing the vulnerability of rangelands to prolonged droughts and climatic changes. Particularly, positive impact of moderate grazing intensity on rangelands functioning is demonstrated by the formation of livestock trampling routes, which transect hillslopes, increase ecosystem geodiversity, and modify the spatial redistribution of scarce water and soil resources at the patch scale. Numerical simulations of a mathematical model for vegetation patterns in water-limited systems show that the trampling routes increase the survivability of vegetation patches under prolonged droughts. In practical terms, the concept of small-scale geodiversity is relevant for the determination, monitoring, and assessment of land degradation, as well as for restoration projects of eroded lands and degraded ecosystems.